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Thermocouple power

Last week there was an interesting debate about raising the altitude of a  
satellite by using magnertic fields.
Carrying on the wacky ideas theme, I've been looking at producing power by  
using thermocouples and not solar cells.
Question: Does anyone know the 'current' or the impedance of the voltage  
source represented by a thermocouple?
A thermocouple generates an emf (voltage) proportional to the difference in  
temperature between its two junctions.
Given that we know a white object in space gets very cold, while   Aluminium 
gets very hot it's interesting looking at the possibility of  thermocouple 
power....Even if it's just to understand its limitations
A thermocouple can be made very small so it should be possible to  
manufacture an array of them in a reasonable space. 
Example:  A junction of two wires, one made from constantan and  one from 
Chromel will generate a voltage of 58 microvolts for every degree  difference 
between the junctions.
That means for a 100 degree C difference you  generate  5.8mV.
For 350 junctions in a chain you generate 2.03 V
and for 6 chains (if you wanted to risk all those junctions in series) you  
could have 12.18V
But.........how much power can you draw from it ??
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